如何使用缓存过期？

Question

I use Speed Up to check the speed of my website and it gives some tips like: "Optimizing Cache". I found some info on yahoo.com like ExpiresDefault "access plus 10 years"

Should I put that rule in the .htaccess?

And another question, should I use that for my website? it's totally not static, it's a very complex browser game with dynamic pages. I found this link: http://www.askapache.com/hacking/speed-site-caching-cache-control.html

But when I cache the media files for one year, and then I update an image, it is not visible for the users for one year?

Answer 1

The html5 boilerplate project has extensive docs on setting up cache headers, and using the standard htaccess file which comes with the project on it's own can give you a great foundation in setting up cache headers correctly.

Cache headers define how long a user can download a file and expect the contents to be fresh. As such you should use short or no cache expiry for dynamic pages. Usually a short expiry for dynamic content is merely a means of managing server load - i.e. you only add short expiry when you're at the point of wanting/needing to reduce communication with your server.

For any url with a long cache expiry, when the contents change so should the url. so

/img/sprite.png

if you modify that file, make it:

/img/sprite_<x>.png

where x is whatever you like - e.g. the date 20120326HHMM

If you use a build process, the above can be automated such that you don't have to think about it. That's also something that's covered at length in the html5 boilerplate docs.